Flexible electro-resistive impact detection sensor for front rail mounted airbag

ABSTRACT

A sensing device for actuating an airbag system in a motor vehicle comprises an airbag having a stowed condition and an inflated condition, an inflator operationally coupled with the airbag responsive to electrical actuation for inflating the airbag with a gas, an impact detection sensor for generating a signal upon an offset impact event, and a controller for processing the signal generated by the sensor and electrically actuating the inflator upon computing a predetermined impact severity to a forward corner of the motor vehicle. The motor vehicle further comprises a front bumper beam attached proximate a distal end of a front rail and the sensor comprises a flexible electro-resistive sensor mounted to a rear side of an outboard portion of the front bumper beam.

CLAIM OF PRIORITY AND CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to currently pending, commonly assignedU.S. application Ser. No. 14/082,443 filed on Nov. 18, 2013, titledFLEXIBLE ELECTRO-RESISTIVE IMPACT DETECTION SENSOR FOR FRONT RAILMOUNTED AIRBAG and is also related to U.S. application Ser. No.14/082,438 now U.S. Pat. No. 9,004,216, issued on Apr. 14, 2015, titled“FRONT RAIL MOUNTED AIRBAG” and U.S. application Ser. No. 14/082,455 nowU.S. Pat. No. 9,127,968 issued on Sep. 8, 2015, titled “FLEXIBLE OPTICALIMPACT DETECTION SENSOR FOR FRONT RAIL MOUNTED AIRBAG,” the contents ofwhich are hereby incorporated by reference in their entirety.

FIELD OF THE INVENTION

The present invention generally relates to an airbag for a motor vehicleto minimize intrusion into the vehicle during an impact event,specifically a front side rail airbag that is triggered to inflate inthe event of and to mitigate small offset rigid barrier impacts.

BACKGROUND OF THE INVENTION

Airbag systems for use in motor vehicles are generally well-known in theart. Traditionally, such airbag systems have been used within motorvehicle interiors to mitigate and reduce occupant impacts with motorvehicle interior components and structures, such as steering wheels,dashboards, knee bolsters, side door panels, and body pillars.

The present disclosure, however, addresses the application of suchairbag systems in combination with exterior motor vehicle components tomanage and control motor vehicle impact events with external objects. Inparticular, the airbag system is adapted to manage and control an impactevent to the front corner of the motor vehicle. That is, various testingprotocols and standards are being and have been developed to addressvehicle integrity in the event of such a collision. For example, theInsurance Institute for Highway Safety (IIHS) has adopted a new smalloffset frontal crash test, where the test objective is to manage andcontrol damage and injuries resulting from actual motor vehicle impactswith stationary rigid poles (offset from the motor vehicle center ofgravity and outside the main longitudinal rail), vehicle to vehiclecollinear offset impacts (again, offset from the motor vehicle center ofgravity), and vehicle to vehicle frontal oblique impacts. The IIHS testprotocol involves the evaluation of such impacts against a rigid poleand currently envisions using a 25 percent overlap rigid barrier with acurved end simulating a 6-inch pole radius. The test impact velocity is40 mph (64 kilometers per hour). The contemplated testing protocol isreferred herein as the 40 mph Small Offset Rigid Barrier (“SORB”) impacttest.

In view of the SORB test protocol, current front end structures arebeing evaluated to optimize vehicle performance in small offset poleimpact events. Hence, solutions for mitigating SORB impacts would beadvantageous.

The airbag assembly disclosed herein particularly accomplishes theforegoing optimization of vehicle performance by providing a deployablestructure mounted to the front side rail of the vehicle behind thebumper. Upon vehicle impact with the SORB, a front bumper mounted sensorsends a signal to an electronic control unit or ECU. Once the signal isprocessed, the ECU activates a side rail mounted inflator deploying theairbag. The airbag design is configured such that the airbag will deployin a triangular shape, preferably creating a 30 degree angle with thelongitudinal axis of the side rail and the motor vehicle. The 30 degreeangular end of the triangular deployed airbag is preferably closest tothe front bumper system of the vehicle. This deployment configurationallows for the vehicle to generate a very high Y-force against the rigidbarrier to propel the vehicle away from the barrier and thus redirectimpact energy by lateral movement of the motor vehicle and therebyminimize vehicle intrusion.

SUMMARY OF THE INVENTION

According to one aspect of the present disclosure, an airbag system isdisclosed that mitigates intrusion in the event of an offset rigidbarrier impact to a forward corner of a motor vehicle. The airbag systemcomprises a motor vehicle front rail having a forward projecting distalend and an airbag attached proximate the distal end of the front rail,the airbag having a stowed condition and an inflated condition, whereinthe airbag in the inflated condition has an inclined angular leadingedge. An inflator is operationally coupled with the airbag and isresponsive to electrical actuation for inflating the airbag with a gas.An impact detection sensor generates a signal upon an impact event,whereby a controller processes the signal generated by the detectionsensor and electrically actuates the inflator upon computing apredetermined impact severity to the forward corner of the motorvehicle. The inclined angular leading edge of the airbag in the inflatedcondition acts against the offset rigid barrier so as to generate alateral force against the offset rigid barrier to push the motor vehicleaway from the barrier and thereby redirect impact energy by lateralmovement of the motor vehicle.

Still another aspect of the present disclosure is an airbag systemhaving a pair of airbags, wherein one of the pair of airbags is mountedon each side of the motor vehicle.

Yet another aspect of the present disclosure is an airbag system whereinthe motor vehicle has a front wheel mounted proximate the front rail,and the airbag is mounted forward of the front wheel.

An additional aspect of the present disclosure is an airbag systemwherein the motor vehicle includes a body panel having an exterior andan interior surface, the airbag being disposed proximate the interiorsurface to act through the body panel to generate the lateral forceagainst the offset rigid barrier.

Another aspect of the present disclosure is an airbag system utilizingan airbag having a substantially triangular configuration when in theinflated condition, where an angular leading edge corresponds to thehypotenuse of the triangular configuration, a forward end of the airbagcorresponds to the apex of the triangular configuration, and a rearwardend corresponds to the base of the triangular configuration.

Still another aspect of the present disclosure is an airbag system wherethe apex of the triangular configuration has an angle of about 30degrees.

A further aspect of the present disclosure is an airbag system, whereinthe motor vehicle is equipped with an automatic occupant restraintsystem having occupant restraint system deployment sensor, and theimpact detection sensor is also the deployment sensor for the automaticoccupant restraint system.

Yet a further aspect of the present disclosure is an airbag systemhaving an impact detection sensor mounted to an interior surface of theoutboard portion of the front bumper.

An additional aspect of the present disclosure is an airbag systemhaving an impact detection sensor that detects bending of the outboardportion of the front bumper during the impact event.

Yet another aspect of the present disclosure is an airbag system havingan impact detection sensor comprised of a conductive film that generatesan electrical signal when bent.

A still further aspect of the present disclosure is an airbag systemhaving an impact detection sensor comprising a fiber optic cable thatgenerates a variable output signal in response to bending of the fiberoptic cable.

Another aspect of the present disclosure is an airbag system for a motorvehicle comprising a front rail, an airbag attached to the front rail,the airbag when inflated having an angular leading edge, an inflator, asensor for generating a signal upon an impact to the corner of thevehicle by an object, and a controller for receiving the signal from thesensor and actuating the inflator, wherein the angular leading edge ofthe airbag generates a lateral force against the object.

A yet additional aspect of the present disclosure is an airbag systemutilizing a front rail having a distal end and an outer side surface,wherein the airbag is attached to the distal end of the front rail onthe outer side surface of the front rail.

A further aspect of the present disclosure is an airbag system utilizinga pair of front rails extending forward from each side of the motorvehicle, with one each of a pair of the airbags is mounted on each ofthe outer side surfaces thereof.

Still another aspect of the present disclosure is a method of employingan airbag system to generate a lateral force against an offset rigidbarrier to push the motor vehicle away from the barrier and therebyredirect impact energy by lateral movement of the motor vehicle, whereinthe method comprises the steps of providing a motor vehicle front railhaving a forward projecting distal end, attaching an airbag proximatethe distal end of the front rail, the airbag having a stowed conditionand an inflated condition, wherein the airbag in the inflated conditioncreates an inclined angular leading edge, equipping the airbag with aninflator operationally coupled with the airbag responsive to electricalactuation for inflating the airbag with a gas, providing an impactdetection sensor for generating a signal upon an impact event, andproviding a controller for processing the signal generated by thedetection sensor, electrically actuating the inflator upon apredetermined impact severity to the forward corner of the motorvehicle, and presenting the inclined angular leading edge of the airbagin the inflated condition to act against the offset rigid barrier so asto generate a lateral force against the offset rigid barrier to push themotor vehicle away from the barrier and thereby redirect impact energyby lateral movement of the motor vehicle.

Yet another aspect of the present disclosure is a method wherein theairbag has a substantially triangular configuration when in the inflatedcondition, wherein the angular leading edge corresponds to thehypotenuse of the triangular configuration, a forward end of the airbagcorresponds to the apex of the triangular configuration having an angleof about 30 degrees, and a rearward end corresponds to the base of thetriangular configuration.

These and other aspects, objects, and features of the present disclosurewill be understood and appreciated by those skilled in the art uponstudying the following specification, claims, and appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a front perspective view of a motor vehicle front side framerail incorporating the first embodiment of the airbag for the airbagsystem in accordance with the present disclosure in the inflatedcondition;

FIG. 2 is a rear perspective view of a motor vehicle front side framerail incorporating the first embodiment of the airbag for the airbagsystem in accordance with the present disclosure in the inflatedcondition;

FIG. 3 is a bottom view of the first embodiment of the airbag for theairbag system of the present disclosure in the inflated condition;

FIG. 4 is a front view of the first embodiment of the airbag in theinflated condition in accordance with the present disclosure;

FIG. 5 is a side view of the first embodiment of the airbag in theinflated condition in accordance with the present disclosure;

FIG. 6 is a front perspective view of a second embodiment of the airbagin the inflated condition in accordance with the present disclosure;

FIG. 7 is a top view of the second embodiment of the airbag in theinflated condition contacting the impact barrier in accordance with thepresent disclosure;

FIG. 8 is a top view of the second embodiment of the airbag in thestowed condition in accordance with the present disclosure;

FIG. 9 is a rear perspective view of the first embodiment of theinstalled bumper bending impact sensor for use with the airbag system ofthe present disclosure;

FIG. 10 is a top perspective view of the first embodiment of the bumperbending impact sensor for use with the airbag system of the presentdisclosure;

FIG. 11a is another perspective view of the first embodiment of thebumper bending impact sensor for use with the airbag system of thepresent disclosure;

FIG. 11b is yet another perspective view of the first embodiment of thebumper bending impact sensor for use with the airbag system of thepresent disclosure;

FIG. 12 is a schematic view of the second embodiment of the bumperbending impact sensor for use with the airbag system of the presentdisclosure;

FIG. 13 is perspective view of the second embodiment of the bumperbending impact sensor for use with the airbag system of the presentdisclosure; and

FIG. 14 is a rear perspective view of the second embodiment of theinstalled bumper bending impact sensor for use with the airbag system ofthe present disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

For purposes of description herein, the terms “upper,” “lower,” “right,”“left,” “rear,” “front,” “vertical,” “horizontal,” and derivativesthereof shall relate to the invention as oriented in FIG. 1. However, itis to be understood that the invention may assume various alternativeorientations and step sequences, except where expressly specified to thecontrary. It is also to be understood that the specific devices andprocesses illustrated in the attached drawings, and described in thefollowing specification, are simply exemplary embodiments of theinventive concepts defined in the appended claims. Hence, specificdimensions and other physical characteristics relating to theembodiments disclosed herein are not to be considered as limiting,unless the claims expressly state otherwise.

Referring to FIGS. 1-4, a motor vehicle 10 includes a front frame 12including a pair of front rails 16 of the motor vehicle. In the oneembodiment of the present disclosure, the front frame 12 may extendsubstantially the length of the body, but in other configurations mayextend outwardly and forward of a unibody body structure of the motorvehicle 10, as is typical of smaller vehicles. Each of the front rails16 may have a beam configuration with integrated ribs 18 and flanges 20for reinforcement, as shown in FIGS. 1-8. The front rails 16 may alsohave a tubular configuration, as shown in FIGS. 9 and 14. In eithercase, each of the front rails 16 include a front distal end 22 providedwith a flange 24, to which a bumper assembly 26 may be attached, eitherdirectly or indirectly through an intermediate bumper bracket 28.

The bumper assembly 26 can adopt one of many possible configurations,but, as is typical, preferably includes a steel reinforcement beam 30 towhich is attached an outer body fascia 32 having a decorative finish andcolor coordinated to the overall exterior color of the motor vehicle 10.The attachment of the bumper assembly 26 to the front rail 16 can alsoinclude a low speed (i.e., 5-9 mph) impact mitigator 154, such as apolygel mitigator having a displaceable ram and tube assembly capable ofabsorbing impact energy from a low speed impact without damage to thedistal end 22 of the front rails 16 and minimal damage to the outer bodyfascia 32, as shown in FIGS. 9 and 14.

The front rails 16, as well as other front body structures and enginecomponents (in the case of front mounted engine motor vehicles) providea deformable forward section 34 (which may also be used for impactmitigation), as is known in the art. It is contemplated and intendedthat the forward section 34 will deform upon contact with an object in aforward collision, such as in the aforementioned NCAP testing, to absorbthe impact energy associated with such a forward collision. As is commonon such systems, one or more accelerometers is used as a sensing deviceto generate an electrical signal upon the sudden de-acceleration of afrontal impact. This signal is then detected by an on-board electroniccontrol unit or ECU 60 and then used to determine whether the installedoccupant restraint system, such as one or more airbag assemblies, shouldbe deployed within the occupant compartment in the event that apredetermined de-acceleration is detected.

A further optimization of vehicle structural performance for SORBimpacts can be obtained by providing a front rail mounted airbag system35 to mitigate intrusion in a 40 mph SORB impact. An airbag 36 ismounted in the stowed condition to an outer surface 38 of the “crashcan” or deformable segment 156 of the distal end 22 of the front siderail 16, as best seen in FIG. 8. The front side rail mounted airbag 36in the stowed condition preferably includes a number of predeterminedfolds 40, 42, 44, 46 to manage deployment, as noted below. Preferably,one each of a pair of the front side rail mounted airbags 36 is disposedforward each of the front wheels 48. Thus, the front side rail mountedairbag 36 is mounted to the front rail 16 of the motor vehicle 10 behindthe front bumper assembly 26. Further, for cosmetic purposes, the motorvehicle 10 may also include a front side body panel 50, such as aforward fender shown in FIG. 7, having an exterior surface 52 and aninterior surface 54, where the airbag 36 is disposed proximate theinterior surface 54 and acts through the body panel 50 to generate alateral force against the SORB barrier 56, as discussed below.

Upon vehicle impact with the SORB barrier 56, a sensor 58 sends a signalto an electronic control unit or ECU 60. Once the signal is processed,the ECU 60 activates an inflator 62 operationally coupled with the frontside rail mounted airbag 36, deploying the front side rail mountedairbag 36. The airbag 36 is preferably configured such that the airbag36 will deploy in a substantially triangular configuration when in theinflated condition, thereby creating an angular leading edge 64corresponding to the hypotenuse of the triangular configuration, aforward end 66 of the airbag corresponding to the apex of the triangularconfiguration and preferably having an angle of about 30 degrees, and arearward end 68 corresponding to the base of the triangularconfiguration. This deployment configuration allows for the vehicle togenerate a very high lateral or Y-force against the SORB barrier 56 topropel the motor vehicle 10 laterally away from the SORB barrier 56 andthus redirect impact energy by lateral movement of the motor vehicle 10and thereby minimize vehicle intrusion, as best shown in FIG. 7.

As shown in FIGS. 6-8, the forward end 66 of the airbag may be extendedlaterally outwardly to form an offset wall 70 in order to fill the spacebetween the folded airbag and the interior surface 54 of the front sidepanel 50. However, it will be noted that the angular leading edge 64 isdisposed at the same approximately 30 degree angle with the longitudinalaxis of the motor vehicle so as to generate the Y-force necessary tolaterally move the motor vehicle 10. Also, as shown in FIG. 6, it may behelpful to mount the stowed airbag 36 within a frame 72, preferablyfabricated from steel or aluminum, to create a reinforced space withinwhich the airbag 36 can be inflated and thus maintain the shape of theangular leading edge 64 when deployed and in contact with the SORBbarrier 56.

As noted previously, accelerometers may be used as a sensing device togenerate an electrical signal upon the sudden de-acceleration of afrontal impact to deploy airbag(s) within the occupant compartment inthe event that a predetermined de-acceleration is detected. Theseaccelerometers may also be employed to signal a vehicle impact with theSORB. However, under certain circumstances, such as small overlapfrontal impacts, the time taken by the traditional frontal impactsensing systems may not be ideal and may not provide adequate time forproper deployment of the disclosed airbag structure. These kinds ofimpacts may need additional sensing systems especially designed forsensing small overlap frontal impacts, depending on vehicle frontstructure, impact velocity, and the object with which the impact occurs.

Thus, preferably a separate front bumper mounted sensor 58 is used tosend a signal to the ECU 60 (such as that shown in FIG. 12) forinflation of the airbag 36 upon impact with a SORB barrier 56,preferably within 5 to 15 milliseconds after the impact event begins.Indeed, the front side rail airbag 36 is preferably fully deployed andin position before front rails 16 and crash can 154 starts deforming(roughly 10 to 20 milliseconds), depending on the vehicle front endstructure. Therefore, in addition to traditional motor vehicle crashsensors, a front bumper mounted sensor 58 for determining bending in thebumper reinforcement beam 30 can be employed to more rapidly send asignal to the ECU 60 assigned to the front bumper mounted sensor 58mounted to an outboard portion of the front bumper. This locationprovides the ideal signal for sensing the SORB impact event, regardlessof sensor design. However, it is a hostile environment, subject totemperatures of 105° C. and salt spray from wheel splash when drivingduring precipitation. Two preferred concepts are one or moreelectro-resistive beam bending sensors 74 mounted on the front bumperbeam or one or more front bumper beam bending sensors 76 based onoptical fiber technologies.

The first concept, a flexible electro-resistive sensor 74, is a flexiblesensor design which monitors for bending of the bumper reinforcing beam30 located behind the front fascia 32. The flexible electro-resistivesensor 74 includes a force-resistive film 78, which consists of aconductive ink 80 printed on a clear plastic membrane 82. The conductiveink 80 changes resistance in response to material stress experiencedwhen the membrane 82 bends. By applying a voltage and measuring thechange, the amount of bending in the flexible electro-resistive sensor74 can be measured, as shown in FIG. 9. Thus, in an impact event, themembrane 82 bends and an electrical signal generated to measure andcompare the actual impact severity against the predetermined impactseverity to determine if airbag 36 actuation is required. If thedeflected signal equals or exceeds a signal level corresponding to apredetermined impact severity, airbag 36 deployment is initiated. Sincethe flexible electro-resistive sensor 74 operates on current levels thatare insufficient to engage automotive grade communication protocol, thecurrent level of the flexible electro-resistive signal 74 must beincreased in a separate step, after which the signal is output atautomotive voltage levels.

The flexible electro-resistive sensor 74 is mounted to a rear surface 31of the outboard portion 33 of the frontal bumper beam 30, forward of thefront frame side rail 16, to detect a small offset impact event thatinitially causes bending only in the outboard portion 33 of the frontbumper beam 30. Such bending occurs only when impacting an object ofsufficient mass to deflect the sheet metal bumper beam 30 and is notsubject to localized, short duration impacts which are largely resonantand does not result in significant displacement in the bumper beam 30.This improves the discrimination capabilities of the flexibleelectro-resistive sensor 74 versus an accelerometer, which is subject tooscillatory signals from vibrations. To provide a timely decisionsignal, the flexible electro-resistive sensor 74 is preferably mounteddirectly to a rear surface 31 of the outboard portion 33 of the frontbumper beam 30, as shown in FIG. 9. This mounting location is superiorto mounting the electro-resistive front bumper beam bending sensor 74 onthe bumper fascia 32, in that the front bumper beam 30 is morestructurally robust than the fascia 32, and does not bend due toincidental impacts with lower mass objects, such as shopping carts andbicycles.

In order for a flexible membrane sensor to function and survive in thisenvironment, the force-resistive film sensor preferably employs aconductive ink 80 that retains its electrical properties at hightemperatures (i.e., above 100° C.). The flexible electro-resistivesensor 74 is also preferably coated with a waterproof, but flexible,coating 86 to protect the ink 80 from water and salt spray, as shown inFIG. 10. The coating 86 may be a separate, solid piece wrapped aroundthe flexible electro-resistive sensor 74 or a tube which surrounds theflexible electro-resistive sensor 74 and is sealed at the ends. Thecoating 86 may be dipped or sprayed over the flexible electro-resistivesensor 74. The coating 86 thus protects the flexible electro-resistivesensor 74 from temperature extremes and liquid exposure that occurs onthe front bumper assembly 26. The coating 86 materials must be flexibleenough when applied that they do not interfere with the bendingproperties of the flexible electro-resistive sensor 74.

In addition, the flexible electro-resistive sensor 74 may be bonded tothe metal of the bumper beam 30 with an adhesive, so the entire lengthof the flexible electro-resistive sensor 74 is fixed and must expand andcontract along with the bumper. However, the different thermal expansioncoefficients of the force-resistive film sensor ink 80 and membrane 82and the sheet metal of the front bumper beam 30 to which it is mountedinduces an inherent drift in the signal with temperature changes, whichcan be significant when compared to the output of the flexibleelectro-resistive sensor 74 when bent. To minimize such drift, theflexible electro-resistive sensor 74 is preferably mounted at fixedpoints along its length. These could be wire clamps 88 attached to theflexible electro-resistive sensor 74 or built into the protectivecoating 86, as shown in FIG. 11a . It could also be a channel 90 rigidlyattached or built into the bumper beam 30, within which the flexibleelectro-resistive sensor 74 loosely lies, as shown in FIG. 11b . Sucharrangement allows the flexible electro-resistive sensor 74 elements,that is, ink 80, membrane 82, and coating 86, to thermally expand andcontract without regard to the thermal expansion and contraction of thefront bumper beam 30, reducing the amount of signal drift incurred fromthe thermal cycling of the system. The flexible electro-resistive sensor74 can thus be utilized for detecting a SORB impact event in a timelymanner. Further, the flexible electro-resistive sensor 74 is relativelylow cost and robust to the environment, maintaining its sensingcapabilities through liquid spray and temperature changes.

Alternatively, a flexible fiber optic sensor 76 may be used to detect anSORB impact. The flexible fiber optic sensor 76 consists of a fiberoptic cable 92, light source 94, photodiode 96, and amplifier 98, asshown in FIG. 12. The light source 94, preferably an infraredlight-emitting diode (LED), sends a light signal through the fiber opticcable fiber 92, which is received by the photodiode 96, preferably aninfrared detector, which in turn outputs an electrical signal from anamplifier 98 proportional to the quantum of light received.

The flexible fiber optic cable 92 consists of a core material 100surrounded by a thin layer of cladding material 102 having a differentindex of refraction than that of the core material 100. Normally, anylight that bounces off the walls 104 of the core material 100 isreflected back into the core material 100 and no light is lost due tobending of the cable. However, if a partial portion of the cladding isremoved to form a bare portion 106 on the core material 100, as shown inFIG. 13, a portion of the light which strikes the wall 104 of the corematerial 100 at an angle will escape the core material 100. Bending theflexible fiber optic cable 92 allows even more light to escape. Thequantum of light striking the photodiode 96 will be thus changed bybeing reduced, and the signal of the photodiode 96 will be changed bybeing reduced, indicating the degree of bending of the fiber optic cable92. Further, if the cladding 102 is removed on only one side of thefiber optic cable 92, the photodiode 96 can be used to detect adirectional signal, indicating whether the fiber optic cable 92 isbending towards the bare portion 106 of the modified side of the fiberoptic cable 92 or away from it.

As noted above, in the SORB test mode, the impact is preferably detectedwithin 5 milliseconds of initial contact in order to provide timelyactivation of the front side rail airbag 36. By carefully placing thefiber optic cable 92 in the area of interest and modifying the cladding102 to produce bare portions 106 in a defined pattern, the flexibleoptical sensor 76 can be adapted to provide a signal to specificallydetect the SORB crash mode. As shown in FIG. 14, the fiber optic cablecan be mounted to the back surface 31 of the outboard portion 33 of thebumper reinforcement beam 30 and also to the distal portion 22 of theframe rail 16 near the flange 24. In this configuration, the flexibleoptical sensor 76 senses any rearward bending of the outboard portion 33of the front bumper assembly 26. In order to accommodate this specificmode, the cladding 102 is removed to form bare portions 106 in specificareas of the fiber optic cable 92. That is, the section of the fiberoptic cable 92 directly mounted to the outboard portion 33 of the frontbumper reinforcement beam 30 preferably has cladding 102 removed to formbare portions on one side at regular intervals to detect any localdeformation of the bumper reinforcement beam 30 outside the frame rail16. The cladding 102 is preferably removed to form bare portions 106 atsmaller intervals in the bend radius to give a timely indication ofdeformation between the bumper reinforcement beam 30 and the front siderail 16 and flange 24. The cladding 102 is preferably only removed inthese sections of the fiber optic cable 92 to form bare portions 106 onone side of the cable in order to differentiate inward bending fromoutward bending.

The detection of the specific SORB impact mode of interest is obtainedby comparing the detected light intensity signal to a predeterminedlight intensity signal corresponding to an impact severity justifyingairbag deployment and deployment of the airbag when the detected lightsignal equals or exceeds the predetermined light intensity signal. Thesection of the fiber optic cable 92 mounted to the front rail 16 has nocladding removed, since the deformation of the front rail 16 will occurtoo late in the event to be of use for activating front side rail airbagsystem 35. Using this selective cladding removal technique, a singlelength of fiber optic cable 92 can be designed to perform timely flexsensing in a specific orientation and direction. The optical cablesensor can be bonded to a rear surface of the front bumper beam with anadhesive along substantially the entire length of the sensor in contactwith the bumper and the front rail. The optical fiber sensor can also bemounted to the rear of the front bumper beam and the distal portion ofthe front rail at fixed points along its length by wire clamps 88attached to the sensor as shown in FIG. 11 a.

The SORB front rail mounted airbag system 35 disclosed herein islightweight, requires minimum packaging, and utilizes well-proveninflator technology. Further, the disclosed SORB front rail mountedairbag system 35 does not interfere with efforts to optimize motorvehicle performance of the New Car Assessment Program (NCAP) 35 mph fullfrontal crash mode. That is, the disclosed SORB front rail mountedairbag system 35 may be deployed in all cases when a frontal crashcomponent may exist (e.g., full frontal, offset frontal and angularimpacts). While the SORB impact event may be sensed by the traditionalfront crash sensors for restraint deployment in frontal crashes,separate front bumper reinforcement beam-mounted sensors 58 providedimproved performance.

It is to be understood that variations and modifications can be made onthe aforementioned structure without departing from the concepts of thepresent invention, and further it is to be understood that such conceptsare intended to be covered by the following claims unless these claimsby their language expressly state otherwise.

We claim:
 1. A sensing device for actuating an airbag system in a motorvehicle comprising an airbag having a stowed condition and an inflatedcondition, an inflator operationally coupled with the airbag responsiveto electrical actuation for inflating the airbag with a gas, an impactdetection sensor for generating a signal upon an offset impact event,and a controller for processing the signal generated by the sensor andelectrically actuating the inflator upon computing a predeterminedimpact severity to a forward corner of the motor vehicle, wherein themotor vehicle further comprises a front bumper beam attached proximate adistal end of a front rail and the sensor comprises a flexibleelectro-resistive sensor mounted to a rear side of an outboard portionof the front bumper beam.
 2. The sensing device of claim 1, wherein thesensor is directly mounted to a rear side of the front bumper beam atthe outboard portion of the front bumper beam and is adapted to measurebending in the front bumper beam.
 3. The sensing device of claim 1,wherein the sensor is attached to a rear surface of the front bumperbeam.
 4. The sensing device of claim 3, wherein the sensor is attachedto a rear surface of the front bumper beam at fixed points along itslength.
 5. The sensing device of claim 4, wherein the sensor is attachedto the rear side of the front bumper beam at fixed points along itslength by wire clamps attached to the sensor.
 6. The sensing device ofclaim 3, wherein the rear surface of the front bumper beam furthercomprises a channel and the sensor is disposed within the channel suchthat the sensor may thermally expand and contract independently of thethermal expansion and contraction of the front bumper beam.
 7. Thesensing device of claim 1, wherein the sensor comprises aforce-resistive film having a conductive ink printed on a plasticmembrane and wherein the conductive ink changes resistance in responseto material stress experienced upon membrane bending.
 8. The sensingdevice of claim 7, wherein a voltage is applied to the sensor andwherein an amount of bending in the sensor is measured to determine anextent of bending in the front bumper beam.
 9. The sensing device ofclaim 8, wherein the sensor generates a signal in response to bending inthe front bumper beam at a signal strength level corresponding to theextent of bending in the front bumper beam and the signal strength levelof the sensor signal is adapted to output at automotive voltage levels.10. The sensing device of claim 7, wherein the conductive ink retainsits electrical properties above 100° C.
 11. The sensing device of claim7, wherein the sensor is coated with a waterproof and flexible coatingto protect the conductive ink.
 12. The sensing device of claim 11,wherein the coating is a separate solid wrapped around the sensor. 13.The sensing device of claim 11, wherein the coating is a tube whichsurrounds the sensor and is sealed at its ends.
 14. The sensing deviceof claim 13, wherein the coating is dipped or sprayed over the sensor.15. The sensing device of claim 1, wherein the sensor comprises aforce-resistive film having a conductive ink printed on a plasticmembrane, wherein the conductive ink changes resistance in response tomaterial stress experienced upon membrane bending to measure and comparean actual impact severity against the predetermined impact severity. 16.An airbag system for a motor vehicle comprising: an airbag having astowed condition and an inflated condition; an inflator operationallycoupled with the airbag responsive to electrical actuation for inflatingthe airbag with a gas; a flexible electro-resistive impact detectionsensor for generating a signal upon an impact event; and a controllerfor processing the signal generated by the sensor and electricallyactuating the inflator upon computing a predetermined impact severity toa forward corner of the motor vehicle, wherein the motor vehicle furthercomprises a front bumper beam attached proximate a distal end of a frontrail and the sensor is mounted to a rear side of an outboard portion ofthe front bumper beam.
 17. A method of deploying a motor vehicle airbagsystem, the method comprising the steps of: providing a motor vehiclefront rail having a forward projecting distal end and a front bumperbeam attached proximate the forward projecting distal end of the frontrail; providing an airbag having a stowed condition and an inflatedcondition equipping the airbag with an inflator operationally coupledwith the airbag responsive to electrical actuation for inflating theairbag with a gas; providing a flexible electro-resistive impactdetection sensor mounted to a rear side of an outboard portion of thefront bumper beam for generating a signal upon an offset impact event;providing a controller for processing the signal generated by thedetection sensor; and electrically actuating the inflator upon apredetermined impact severity to the vehicle.
 18. The method of claim17, further comprising the steps of applying a voltage to the sensor andmeasuring an amount of bending in the sensor to determine an extent ofbending in the front bumper beam.
 19. The method of claim 17, whereinthe sensor comprises a force-resistive film having a conductive inkprinted on a plastic membrane and wherein the conductive ink changesresistance in response to material stress experienced upon membranebending, the method further comprising the step of comparing an actualimpact severity against the predetermined impact severity and deployingthe airbag if the impact severity is equal to or exceeds thepredetermined impact severity.
 20. The method of claim 17, furthercomprising the step of increasing the current level of the signal, afterwhich the signal is output at automotive voltage levels.